Previous methods for bonding wafers made of silicon and silicon oxide (including silica, fused or vitreous, glass, and silica and silicate polymorphs) usually require mechanical compression by direct physical contact at high temperatures. Additionally, achieving physical bonding strength above the intrinsic breakage point of the bondable materials typically requires deposition or plasma/sputtering/dry etching processing of the wafer bonds. The resulting bonds are susceptible to percolation in saline solutions, brittleness of the combined material and strain build-up from volume expansion. Shattering could occur from the 40% volume expansion and thermal mismatch between the Silica and Si(100) phases. Furthermore, desorption of any surface contaminants and/or adsorbates during processing at temperatures as low as 50° C. (at least above the dew point), can result in micro-pressure build-up, which can lead to shattering or delamination of bonded substrates.
The shape, size and contour of the devices and wafers determine the application and cost of the bonding technology. Many bonding technologies requires cumbersome and expensive dies and containers that were needed to be specifically designed and constructed in order to compress wafers which then limited production of volume and variety.
Since many biosensors, solar cells, and glass panel photovoltaic panels are typically based on silica wafers (including but not limited to borosilicate, alpha-quartz) and Si(100) wafers, there exists a need in the art for improved methods for bonding the same together. In particular, there exists a need for methods that can provide hermetically sealed devices, which may be implanted into the human body. Specifically, the need would be to improve the bonding temperature and pressure and the variety of materials to suit the requirements of biological implants.